#!/usr/bin/env python3
''' Calculates the Frechet Inception Distance (FID) to evalulate GANs.
The FID metric calculates the distance between two distributions of images.
Typically, we have summary statistics (mean & covariance matrix) of one
of these distributions, while the 2nd distribution is given by a GAN.
When run as a stand-alone program, it compares the distribution of
images that are stored as PNG/JPEG at a specified location with a
distribution given by summary statistics (in pickle format).
The FID is calculated by assuming that X_1 and X_2 are the activations of
the pool_3 layer of the inception net for generated samples and real world
samples respectivly.
See --help to see further details.
'''
from __future__ import absolute_import, division, print_function
import numpy as np
import os
import gzip, pickle
import tensorflow as tf
from scipy.misc import imread
from scipy import linalg
import pathlib
import urllib
import tarfile
import warnings
MODEL_DIR = '/tmp/imagenet'
DATA_URL = 'http://download.tensorflow.org/models/image/imagenet/inception-2015-12-05.tgz'
pool3 = None
class InvalidFIDException(Exception):
pass
#-------------------------------------------------------------------------------
def get_fid_score(images, images_gt):
images = np.stack(images, 0)
images_gt = np.stack(images_gt, 0)
with tf.Session() as sess:
m1, s1 = calculate_activation_statistics(images, sess)
m2, s2 = calculate_activation_statistics(images_gt, sess)
fid_value = calculate_frechet_distance(m1, s1, m2, s2)
print("Obtained fid value of {}".format(fid_value))
return fid_value
def create_inception_graph(pth):
"""Creates a graph from saved GraphDef file."""
# Creates graph from saved graph_def.pb.
with tf.gfile.FastGFile( pth, 'rb') as f:
graph_def = tf.GraphDef()
graph_def.ParseFromString( f.read())
_ = tf.import_graph_def( graph_def, name='FID_Inception_Net')
#-------------------------------------------------------------------------------
# code for handling inception net derived from
# https://github.com/openai/improved-gan/blob/master/inception_score/model.py
def _get_inception_layer(sess):
"""Prepares inception net for batched usage and returns pool_3 layer. """
layername = 'FID_Inception_Net/pool_3:0'
pool3 = sess.graph.get_tensor_by_name(layername)
ops = pool3.graph.get_operations()
for op_idx, op in enumerate(ops):
for o in op.outputs:
shape = o.get_shape()
if shape._dims != []:
shape = [s.value for s in shape]
new_shape = []
for j, s in enumerate(shape):
if s == 1 and j == 0:
new_shape.append(None)
else:
new_shape.append(s)
o.__dict__['_shape_val'] = tf.TensorShape(new_shape)
return pool3
#-------------------------------------------------------------------------------
def get_activations(images, sess, batch_size=50, verbose=False):
"""Calculates the activations of the pool_3 layer for all images.
Params:
-- images : Numpy array of dimension (n_images, hi, wi, 3). The values
must lie between 0 and 256.
-- sess : current session
-- batch_size : the images numpy array is split into batches with batch size
batch_size. A reasonable batch size depends on the disposable hardware.
-- verbose : If set to True and parameter out_step is given, the number of calculated
batches is reported.
Returns:
-- A numpy array of dimension (num images, 2048) that contains the
activations of the given tensor when feeding inception with the query tensor.
"""
# inception_layer = _get_inception_layer(sess)
d0 = images.shape[0]
if batch_size > d0:
print("warning: batch size is bigger than the data size. setting batch size to data size")
batch_size = d0
n_batches = d0//batch_size
n_used_imgs = n_batches*batch_size
pred_arr = np.empty((n_used_imgs,2048))
for i in range(n_batches):
if verbose:
print("\rPropagating batch %d/%d" % (i+1, n_batches), end="", flush=True)
start = i*batch_size
end = start + batch_size
batch = images[start:end]
pred = sess.run(pool3, {'ExpandDims:0': batch})
pred_arr[start:end] = pred.reshape(batch_size,-1)
if verbose:
print(" done")
return pred_arr
#-------------------------------------------------------------------------------
def calculate_frechet_distance(mu1, sigma1, mu2, sigma2, eps=1e-6):
"""Numpy implementation of the Frechet Distance.
The Frechet distance between two multivariate Gaussians X_1 ~ N(mu_1, C_1)
and X_2 ~ N(mu_2, C_2) is
d^2 = ||mu_1 - mu_2||^2 + Tr(C_1 + C_2 - 2*sqrt(C_1*C_2)).
Stable version by Dougal J. Sutherland.
Params:
-- mu1 : Numpy array containing the activations of the pool_3 layer of the
inception net ( like returned by the function 'get_predictions')
for generated samples.
-- mu2 : The sample mean over activations of the pool_3 layer, precalcualted
on an representive data set.
-- sigma1: The covariance matrix over activations of the pool_3 layer for
generated samples.
-- sigma2: The covariance matrix over activations of the pool_3 layer,
precalcualted on an representive data set.
Returns:
-- : The Frechet Distance.
"""
mu1 = np.atleast_1d(mu1)
mu2 = np.atleast_1d(mu2)
sigma1 = np.atleast_2d(sigma1)
sigma2 = np.atleast_2d(sigma2)
assert mu1.shape == mu2.shape, "Training and test mean vectors have different lengths"
assert sigma1.shape == sigma2.shape, "Training and test covariances have different dimensions"
diff = mu1 - mu2
# product might be almost singular
covmean, _ = linalg.sqrtm(sigma1.dot(sigma2), disp=False)
if not np.isfinite(covmean).all():
msg = "fid calculation produces singular product; adding %s to diagonal of cov estimates" % eps
warnings.warn(msg)
offset = np.eye(sigma1.shape[0]) * eps
covmean = linalg.sqrtm((sigma1 + offset).dot(sigma2 + offset))
# numerical error might give slight imaginary component
if np.iscomplexobj(covmean):
if not np.allclose(np.diagonal(covmean).imag, 0, atol=1e-3):
m = np.max(np.abs(covmean.imag))
raise ValueError("Imaginary component {}".format(m))
covmean = covmean.real
tr_covmean = np.trace(covmean)
return diff.dot(diff) + np.trace(sigma1) + np.trace(sigma2) - 2 * tr_covmean
#-------------------------------------------------------------------------------
def calculate_activation_statistics(images, sess, batch_size=50, verbose=False):
"""Calculation of the statistics used by the FID.
Params:
-- images : Numpy array of dimension (n_images, hi, wi, 3). The values
must lie between 0 and 255.
-- sess : current session
-- batch_size : the images numpy array is split into batches with batch size
batch_size. A reasonable batch size depends on the available hardware.
-- verbose : If set to True and parameter out_step is given, the number of calculated
batches is reported.
Returns:
-- mu : The mean over samples of the activations of the pool_3 layer of
the incption model.
-- sigma : The covariance matrix of the activations of the pool_3 layer of
the incption model.
"""
act = get_activations(images, sess, batch_size, verbose)
mu = np.mean(act, axis=0)
sigma = np.cov(act, rowvar=False)
return mu, sigma
#-------------------------------------------------------------------------------
#-------------------------------------------------------------------------------
# The following functions aren't needed for calculating the FID
# they're just here to make this module work as a stand-alone script
# for calculating FID scores
#-------------------------------------------------------------------------------
def check_or_download_inception(inception_path):
''' Checks if the path to the inception file is valid, or downloads
the file if it is not present. '''
INCEPTION_URL = 'http://download.tensorflow.org/models/image/imagenet/inception-2015-12-05.tgz'
if inception_path is None:
inception_path = '/tmp'
inception_path = pathlib.Path(inception_path)
model_file = inception_path / 'classify_image_graph_def.pb'
if not model_file.exists():
print("Downloading Inception model")
from urllib import request
import tarfile
fn, _ = request.urlretrieve(INCEPTION_URL)
with tarfile.open(fn, mode='r') as f:
f.extract('classify_image_graph_def.pb', str(model_file.parent))
return str(model_file)
def _handle_path(path, sess):
if path.endswith('.npz'):
f = np.load(path)
m, s = f['mu'][:], f['sigma'][:]
f.close()
else:
path = pathlib.Path(path)
files = list(path.glob('*.jpg')) + list(path.glob('*.png'))
x = np.array([imread(str(fn)).astype(np.float32) for fn in files])
m, s = calculate_activation_statistics(x, sess)
return m, s
def calculate_fid_given_paths(paths, inception_path):
''' Calculates the FID of two paths. '''
inception_path = check_or_download_inception(inception_path)
for p in paths:
if not os.path.exists(p):
raise RuntimeError("Invalid path: %s" % p)
create_inception_graph(str(inception_path))
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
m1, s1 = _handle_path(paths[0], sess)
m2, s2 = _handle_path(paths[1], sess)
fid_value = calculate_frechet_distance(m1, s1, m2, s2)
return fid_value
def _init_inception():
global pool3
if not os.path.exists(MODEL_DIR):
os.makedirs(MODEL_DIR)
filename = DATA_URL.split('/')[-1]
filepath = os.path.join(MODEL_DIR, filename)
if not os.path.exists(filepath):
def _progress(count, block_size, total_size):
sys.stdout.write('\r>> Downloading %s %.1f%%' % (
filename, float(count * block_size) / float(total_size) * 100.0))
sys.stdout.flush()
filepath, _ = urllib.request.urlretrieve(DATA_URL, filepath, _progress)
print()
statinfo = os.stat(filepath)
print('Succesfully downloaded', filename, statinfo.st_size, 'bytes.')
tarfile.open(filepath, 'r:gz').extractall(MODEL_DIR)
with tf.gfile.FastGFile(os.path.join(
MODEL_DIR, 'classify_image_graph_def.pb'), 'rb') as f:
graph_def = tf.GraphDef()
graph_def.ParseFromString(f.read())
_ = tf.import_graph_def(graph_def, name='')
# Works with an arbitrary minibatch size.
with tf.Session() as sess:
pool3 = sess.graph.get_tensor_by_name('pool_3:0')
ops = pool3.graph.get_operations()
for op_idx, op in enumerate(ops):
for o in op.outputs:
shape = o.get_shape()
if shape._dims != []:
shape = [s.value for s in shape]
new_shape = []
for j, s in enumerate(shape):
if s == 1 and j == 0:
new_shape.append(None)
else:
new_shape.append(s)
o.__dict__['_shape_val'] = tf.TensorShape(new_shape)
if pool3 is None:
_init_inception()